Shaft axial compliance mechanism

ABSTRACT

A hermetic compressor assembly including a compressor housing has a motor and a compression mechanism mounted therein, operatively coupled by a drive shaft having a substantially horizontal axis of rotation. A bearing housing is connected to the motor and receives a portion of the drive shaft having a bearing assembly affixed thereto. A retaining element is received in a groove formed in the bearing housing and is in abutting contact with the bearing assembly to prevent relative movement of the drive shaft in both directions along the axis of rotation.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to hermetic compressors andparticularly to those having substantially horizontal drive shafts.

[0002] Conventionally, hermetic compressors include a hermeticallysealed housing having a compression mechanism and an electric motordisposed therein. The compression mechanism and motor are operativelycoupled by a drive shaft. A substantially horizontal hermetic compressoris one in which the shaft axis of rotation and thus the drive shaft arenearly horizontal. Electrical power is provided to the motor through ahermetic terminal assembly to induce rotation of the drive shaft whichin turn induces rotation of the compression mechanism. As thecompression mechanism operates, refrigerant fluid is compressed thereinto a discharge pressure and is exhausted as refrigerant gas to arefrigeration system.

[0003] Particularly with horizontal compressors, the weight of the driveshaft and the rotor does not urge the drive shaft along its axis ofrotation into a position in which the drive shaft is in abuttingrelationship with a thrust bearing surface. During operation of thecompressor, the rotation of the rotor, drive shaft, and compressionmechanism may generate oscillating axial movement of the drive shaft.Such back and forth oscillation of the drive shaft is often accompaniedby objectionable noise, such as knocking.

[0004] One method of biasing the rotor and drive shaft in one directionalong the longitudinal shaft axis of rotation is by using the solenoideffect of the motor. The stator and the rotor of the motor are offset bya specific distance, and upon energization of the stator, the rotor isurged in a direction along the longitudinal shaft axis of rotation toallow alignment of its laminae with those of the stator. The rotorexerts an axial force on the drive shaft, moving the drive shaft intoengagement with a thrust bearing surface to maintain axial compliance ofthe drive shaft during compressor operation. When using the solenoideffect of the motor to bias the rotor and the drive shafts, axialpositioning of the rotor and the stator must be closely toleranced.

[0005] An additional method which may be used to prevent axialoscillations of the drive shaft includes constructing the compressor tohave close tolerances and selective fits. By constructing the compressorin such a manner, the available space in which the drive shaft may moveis limited, thus limiting axial movement of the drive shaft. Therefore,the amount of noise produced by oscillating axial movement of the driveshaft is reduced.

[0006] A problem with these methods of providing axial compliance of ahorizontal drive shaft is that gauging and selective assembly ofcompressor components is labor intensive. Further, manufacturingprocesses for compressor components having close tolerances are moredifficult and thus more expensive.

[0007] Further means for limiting axial movement of the drive shaft isdescribed in pending U.S. patent application Ser. No. 09/849,541,assigned to the assignee of the present invention, the disclosure ofwhich is expressly incorporated herein by reference. Those means includeproviding a circumferential groove near one end of the shaft. A bore isprovided in the outboard bearing supporting one end of the drive shaft,aligning with the circumferential groove. A retaining element ispositioned in both the bore and shaft circumferential groove such that aportion of the retaining element is located within each of the bore andthe groove. The retaining element thereby prevents relative axialmovement of the drive shaft.

[0008] A problem with such means for limiting axial movement of thedrive shaft is that complex machining of the drive shaft and outboardbearing to receive a retaining element is labor intensive and requiresadditional steps in the manufacturing process, thus increasingmanufacturing costs.

[0009] It is desired to provide a shaft axial compliance mechanism for asubstantially horizontal hermetic compressor which simplifies machiningand assembly of the compressor components to prevent objectionable noisecreated by oscillating axial movement of the drive shaft.

SUMMARY OF THE INVENTION

[0010] The present invention provides a shaft compliance mechanism for asubstantially horizontal hermetic compressor to prevent objectionablenoise created by oscillating axial movement of the drive shaft.

[0011] The substantially horizontal compressor of the present inventionincludes a housing having a motor and a compression mechanism locatedtherein, and operatively coupled by a drive shaft. A bearing housing isaffixed to the motor and includes a collar in which one end of the driveshaft is rotatably supported. A bearing assembly is shrink fitted ontoan end of the drive shaft. The bearing/drive shaft assembly is insertedinto a cavity defined in the collar of the bearing housing. The bearinghousing is further provided with a circumferential groove in which aretaining element such as an annular snap ring is positioned to maintainthe axial position of the bearing assembly, and thus the drive shaftwithin the bearing housing. The retaining element prevents oscillatingaxial movement of the drive shaft, and thus reduces objectionable noisecreated by such movement.

[0012] The present invention provides a hermetic compressor assemblyincluding a compressor housing having a compression mechanism and amotor disposed therein. A drive shaft having an axis of rotationoperatively couples the compression mechanism and the motor. A bearinghousing is connected to the motor. A bearing assembly is affixed to thedrive shaft with the bearing assembly and the drive shaft being receivedin the bearing housing. A retaining element connected to the bearinghousing is in abutting contact with the bearing assembly to preventrelative movement of the drive shaft in both directions along the axisof rotation.

[0013] The present invention further provides a hermetic compressorassembly having a compressor housing in which a compression mechanismand motor are disposed. The compression mechanism and motor areoperatively coupled by a drive shaft having an axis of rotation. Abearing assembly is affixed to the drive shaft, the bearing assembly andthe drive shaft being received in a bearing housing connected to themotor. A circumferential groove is formed in the bearing housing and aretaining element received therein. The retaining element is in abuttingcontact with the bearing assembly to prevent relative movement of thedrive shaft in both directions along the axis of rotation.

[0014] The present invention also provides a hermetic compressorassembly including a compressor housing in which a compression mechanismand a motor are disposed. A drive shaft having an axis of rotationoperatively couples the compression mechanism and the motor. A bearinghousing is connected to the motor. Further provided are shaft axialcompliance means engaging the drive shaft and the bearing housing toprevent relative movement of the drive shaft in both directions alongthe shaft axis of rotation.

[0015] The present invention provides a method of preventing oscillatingaxial movement of a drive shaft in a hermetic compressor. The methodincludes attaching a bearing housing to a motor of the compressor;affixing a bearing assembly to one end of a drive shaft; positioning thebearing assembly and drive shaft in the bearing housing; and engaging acircumferential groove formed in the bearing housing with a retainingelement, the retaining element in abutting contact with the bearingassembly, to prevent relative movement of the drive shaft.

[0016] An advantage of the present invention is that the tolerances ofthe compressor may be looser and selective component assembly is notrequired to provide axial compliance of the horizontal drive shaft.Further, complex machining and assembly of parts is eliminated, allowingfor axial compliance of the drive shaft with minimal increases in costand labor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention itself will be better understood by reference to thefollowing description of the embodiment of the invention taken inconjunction with the accompanying drawings, wherein:

[0018]FIG. 1 is a sectional side view of a compressor assembly inaccordance with the present invention; and

[0019]FIG. 2 is a fragmentary sectional view of the compressor assemblyof FIG. 1.

[0020] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate an embodiment of the invention, and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Referring to FIG. 1, hermetic compressor assembly 20 includeshousing 22 having end portions 24 and 26 with central portion 28 locatedtherebetween. Housing portions 24, 26, and 28 are hermetically sealed at30 by any suitable process including welding, brazing, or the like.Compressor 20 is arranged substantially horizontally and is supported bymounting bracket 32 and stand 34 located at opposite ends of compressorhousing 22. One end of compressor 20 may be slightly higher than theother to influence the flow of oil in oil sump 35 located withincompressor housing 22 toward oil pick-up tube 92.

[0022] Located within housing 22 is electric motor 36 including stator38 and rotor 40. Located centrally in rotor 40 is aperture 42 in whichdrive shaft 44 is shrink fitted. End 46 of drive shaft 44 is rotatablysupported in collar 48 of bearing housing 50. Bearing housing 50includes substantially cylindrical portion 52 with a plurality ofradially extending arms 54 extending between cylindrical portion 52 andcollar 48. Edge 56 of cylindrical portion 52 is affixed to motor 36 byany suitable method including fasteners such as bolts.

[0023] Operatively coupled to end 58 of drive shaft 44 is compressionmechanism 60 which is illustrated as being a scroll-type compressionmechanism. However, the present invention may be suitably adapted to anyother type of compressor, such as, e.g., a rotary compressor. Thegeneral operation of a scroll compressor is described in U.S. Pat. Nos.5,306,126 and 6,139,294, the disclosures of which are hereby expresslyincorporated herein by reference. The general operation of a rotarycompressor is described in U.S. Pat. No. 5,222,885, the disclosure ofwhich is hereby expressly incorporated herein by reference. Each ofthese references is assigned to the assignee of the present invention.

[0024] Scroll compression mechanism 60 includes fixed scroll member 62,orbiting scroll member 64, and main bearing frame member 66. Fixedscroll member 62 is secured to main bearing frame member 66 by anysuitable method including mounting bolts. Fixed scroll member 62includes flat plate 72 having scroll wrap 74 extending approximatelyperpendicularly therefrom. Orbiting scroll member 64 is fixedly mountedto roller 68 which is secured to offset crank pin 70 formed at end 58 ofdrive shaft 44. Orbiting scroll member 64 includes flat plate 76 havingscroll wrap 78 extending approximately perpendicularly therefrom whichintermeshes with scroll wrap 74 when assembled with fixed scroll member62. Further, back surface 80 of flat plate 76 engages main bearing framemember 66 at thrust bearing surface member 82 while the compressor is ina de-energized or inoperative state.

[0025] Bearings are provided between interfacing surfaces of drive shaft44, scroll compression mechanism 60, main bearing frame member 66, androller 68. Specifically, bearing 84 is located between the outer surfaceof roller 68 and surface 86 of orbiting scroll member 64 and bearing 88is positioned between interfacing surfaces of roller 68 and crank pin70. Bearing 90 is located between main bearing frame member 66 and driveshaft 44. During compressor operation, oil is provided to compressionmechanism 60 and bearings 84, 88, and 90 from oil sump 35. Oil pick-uptube 92 is secured to plate 94 which is attached to collar 48 viafastener 96 and extends into oil sump 35 (FIGS. 1 and 2). Oil pumpassembly 98 is attached to end 46 of drive shaft 44 for rotationtherewith and causes lubricating oil to travel along oil pickup tube 92as drive shaft 44 rotates. From oil pick-up tube 92, oil flows into oilpassageway 100 longitudinally extending through drive shaft 44 to aplurality of passageways (not shown) radially extending from oilpassageway 100 to supply compression mechanism 60, and bearings 84, 88,and 90 with oil.

[0026] During compressor operation, motor 36 is energized which inducesrotation of rotor 40 and thus drive shaft 44. Cylindrical roller 68surrounding offset crank pin 70 rotates with drive shaft 44 to generaterotation of orbiting scroll member 64 with respect to fixed scrollmember 62. A biasing force acts upon orbiting scroll member 64 to moveit axially toward fixed scroll member 62 so that tips 102 and 104 ofscroll wraps 74 and 78 sealingly engage scroll member flat plates 76 and72, respectively, to define a plurality of compression chambers 106.

[0027] Refrigerant fluid at suction pressure is drawn into compressionchambers 106 from a refrigeration system (not shown). As orbiting scrollmember 64 is rotated with respect to fixed scroll member 62, refrigerantfluid captured within compression chambers 106 is compressed todischarge pressure. The refrigerant fluid progresses radially inwardlytoward discharge port 108 located in fixed scroll member 62. Arefrigerant gas flows through discharge port 108 into discharge chamber110 which occupies the interior of compressor housing 22. The dischargepressure fluid is then exhausted through discharge tube 112 back intothe refrigerant system.

[0028] During compressor operation, rotation of drive shaft 44 andcompression mechanism 60 may produce axial movement of drive shaft 44.In a substantially vertically oriented compressor, gravity acts alongthe longitudinal axis of rotation of the drive shaft and the rotor tomaintain seating of the drive shaft with respect to an outboard bearing,for example. In a substantially horizontally arranged compressor 20,gravity does not influence axial movement of drive shaft 44. Oscillatingaxial movement of drive shaft 44 produces objectionable noise, such asknocking, during compressor operation. In order to counteract thesemovements of drive shaft 44, a shaft axial compliance mechanism inaccordance with the present invention is provided.

[0029] Referring to FIGS. 1 and 2, end 46 of drive shaft 44 is rotatablysupported in collar 48 of bearing housing 50. Both drive shaft 46 andbearing housing 50 are engaged by shaft axial compliance mechanism 114which prevents relative movement of drive shaft 44 in both directionsalong shaft axis of rotation 45. Shaft axial compliance mechanism 114includes bearing assembly 116, circumferential groove 118 located incollar 48, and retaining element 120.

[0030] Collar 48 includes first portion 122 and second portion 124extending in opposite directions, perpendicularly to radially extendingarms 54. First collar portion 122 is provided with cavity 126 which isconcentric with aperture 128 extending through second collar portion124. End 46 of drive shaft 44 is received in aperture 128 and shaftaxial compliance mechanism 114 is located in cavity 126.

[0031] Bearing assembly 116 of shaft axial compliance mechanism 114 isaffixed to drive shaft 44 near end 46 to rotatably support drive shaft44 in cavity 126. Bearing assembly 116 is an annular, single row ballbearing assembly including inner race 130, outer race 132, and ballbearings 134. Inner and outer races 130 and 132 are each provided withsemicircular groove 136 which align to receive a plurality of ballbearings 134. Bearing assembly 116 is shrink fitted onto end 46 of driveshaft 44 at drive shaft stepped portion 138.

[0032] Drive shaft 44, having bearing assembly 116 affixed thereto, isreceived in cavity 126 located in collar 48 with opposite axial ends140, 142 of outer race 132 in abutting contact with both collar 48 andretaining element 120. Bearing housing 50 is provided with annularsurface 144 on which outer race 132 of bearing assembly 116 is seatedwith end 140 contacting surface 144. Circumferential groove 118 isformed in first collar portion 122 a distance away from surface 144approximately equal to the axial distance between ends 140, 142 of outerrace 132. Retaining element 120 is positioned within groove 118,extending inwardly to cover a portion of outer race 132 and with lowersurface 146 of retaining element 120 in abutting contact end 142 ofouter race 132. Retaining element 120 may be any suitable elementincluding an annular snap ring, for example, constructed from anysuitable material able to withstand forces acting on element 120 bybearing assembly 116 created during compressor operation when driveshaft 44 attempts to oscillate axially along shaft axis of rotation 45.Retaining element 120 thus maintains the seated position of bearingassembly 116 and prevents axial movement of drive shaft 44 along shaftaxis of rotation 45.

[0033] In assembly, bearing assembly 116 is heated so that the diameterof bearing assembly 116 increases to receive stepped portion 138 ofdrive shaft 44. Bearing assembly 116 is then allowed to cool to providea shrink fit between inner race 130 and drive shaft 44. Drive shaft 44,having bearing assembly 116 secured thereto, is then received in cavity126 of collar 48 with axial end 140 being seated against surface 144formed in first collar portion 122 of collar 48. Retaining element orsnap ring 120 is inserted into circumferential groove 118 in contactwith axial end 142 of outer race 132.

[0034] During compressor operation, retaining element 120 maintains theseated position of bearing assembly 116 and thus prevents axialoscillating movement of drive shaft 44. Shaft axial compliance mechanism114 therefore provides a simple, inexpensive device for eliminatingoscillating axial movement of drive shaft 44 and objectionable noise,such as knocking, associated therewith in substantially horizontallyoriented compressor 20.

[0035] While this invention has been described as having an exemplarydesign, the present invention can be further modified within the spiritand scope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A hermetic compressor assembly, comprising: acompressor housing; a compression mechanism disposed in said housing; amotor disposed in said housing; a drive shaft operatively coupling saidcompression mechanism and said motor, and an axis of rotation; a bearinghousing connected to said motor; a bearing assembly affixed to saiddrive shaft, said bearing assembly and said drive shaft received in saidbearing housing; and a retaining element connected to said bearinghousing in abutting contact with said bearing assembly, whereby relativemovement of said drive shaft in both directions along said axis ofrotation is prevented.
 2. The compressor of claim 1, wherein saidbearing housing further comprises a circumferential groove, a portion ofsaid retaining element received in said groove.
 3. The compressor ofclaim 1, wherein said bearing assembly is shrink fitted onto an end ofsaid drive shaft.
 4. The compressor of claim 1, wherein said bearingassembly further comprises an inner race, an outer race, and at leastone ball bearing located between said inner and outer races.
 5. Thecompressor of claim 4, wherein said bearing housing further comprises anannular surface, said bearing assembly seated against said surface. 6.The compressor of claim 5, wherein said outer race further comprises twoends, one of said ends in abutting contact with said annular surface,and one of said ends in abutting contact with said retaining element. 7.The compressor of claim 1, wherein said retaining element is a snapring.
 8. A hermetic compressor assembly, comprising: a compressorhousing; a compression mechanism disposed in said housing; a motordisposed in said housing; a drive shaft operatively coupling saidcompression mechanism and said motor, and an axis of rotation; a bearinghousing connected to said motor; a bearing assembly affixed to saiddrive shaft, said bearing assembly and said drive shaft received in saidbearing housing; a circumferential groove formed in said bearinghousing; and a retaining element received in said circumferentialgroove, said retaining element in abutting contact with said bearingassembly, whereby relative movement of said drive shaft in bothdirections along said axis of rotation is prevented.
 9. The compressorof claim 8, wherein said bearing assembly is shrink fitted onto an endof said drive shaft.
 10. The compressor of claim 8, wherein said bearingassembly further comprises an inner race, an outer race, and at leastone ball bearing located between said inner and outer races.
 11. Thecompressor of claim 10, wherein said bearing housing further comprisesan annular surface, said bearing assembly seated against said surface.12. The compressor of claim 11, wherein said outer race furthercomprises two ends, one of said ends in abutting contact with saidannular surface, and one of said ends in abutting contact with saidretaining element.
 13. The compressor of claim 8, wherein said retainingelement is a snap ring.
 14. A hermetic compressor assembly, comprising:a compressor housing; a compression mechanism disposed in said housing;a motor disposed in said housing; a drive shaft operatively couplingsaid compression mechanism and said motor, and an axis of rotation; abearing housing connected to said motor; and shaft axial compliancemeans engaging said drive shaft and said bearing housing, wherebyrelative movement of said drive shaft in both directions along saidshaft axis of rotation is prevented.
 15. The compressor of claim 14,wherein said shaft axial compliance means includes a bearing assemblyaffixed to said drive shaft, said bearing assembly and said drive shaftreceived in said bearing housing.
 16. The compressor of claim 15,wherein said shaft axial compliance means includes a circumferentialgroove formed in said bearing housing, a retaining element received insaid groove, said retaining element in abutting contact with saidbearing assembly.
 17. The compressor of claim 15, wherein said bearingassembly is shrink fitted onto an end of said drive shaft.
 18. Thecompressor of claim 16, wherein said bearing assembly further comprisestwo ends, one of said ends in abutting contact with said bearinghousing, and one of said ends in abutting contact with said retainingelement.
 19. The compressor of claim 16, wherein said retaining elementis a snap ring.
 20. A method of preventing oscillating axial movement ofa drive shaft in a hermetic compressor comprising: attaching a bearinghousing to a motor of the compressor; affixing a bearing assembly to oneend of a drive shaft; positioning the bearing assembly and drive shaftin the bearing housing; and engaging a circumferential groove formed inthe bearing housing with a retaining element, the retaining element inabutting contact with the bearing assembly, whereby relative movement ofthe drive shaft is prevented.